The present invention relates to an apparatus and method to remove solid materials from a body of liquid and more particularly but not exclusively, to the removal of fine solids from raw sewage.
Described in Australian patents 728181 and 727926 are methods and apparatus for separating solids from flowing liquids or gases. The apparatus particularly employ screens formed of expanded metal mesh over which the liquid passes under controlled hydraulic conditions. The liquid passes through the mesh while solid materials entrained in the liquid are retained by the mesh. Movement of liquid over the expanded metal mesh provides a washing effect, which ensures that there is no attachment of solids to the screen so that the liquid may pass therethrough and that no blinding of the screen occurs as a result. These apparatus are particularly adapted to remove gross solids from liquids at high flow rates.
The above-described apparatus cannot be easily applied to the separation of fine solids or solids of neutral density, which either tend to pass through or accumulate in the apertures of the screen and result in blinding thereof.
It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages.
There is disclosed herein an apparatus to remove solid material from a body of liquid, said apparatus including:
a wall providing a chamber to receive the liquid, said wall including an apertured portion through which the liquid leaves the chamber, the apertured portion being adapted to remove solid material greater than a predetermined size from liquid passing through the apertured portion;
a housing generally surrounding said wall and co-operating therewith to provide a space into which the liquid flows from said wall;
liquid drive means to at least partly cause movement of the liquid in the chamber so that liquid passes the apertured portion to aid in removing solid material therefrom; and
means to remove the solid material from within the chamber; and
an outlet extending from said space so as to maintain a level of liquid in said space.
Preferably, said wall includes a side wall of a cylindrical configuration with substantially the entire wall providing said apertured portion. Preferably, the cylindrical wall is made of expanded metal mesh.
Preferably, the means to cause movement of liquid in the chamber moves the liquid angularly about the longitudinal axis of the cylindrical wall.
Preferably, the cylindrical wall is movably mounted for angular movement about said axis, and the apparatus includes means to direct a stream of fluid tangentially toward said cylindrical wall.
Preferably, the liquid drive means augments movement of the incoming liquid and is an impeller rotated about the axis of the cylindrical wall.
Preferably, said apparatus is adapted to receive flocculated sewage, with the apparatus including a threshold member above which floc material passes to be removed from the chamber. Preferably, a scraper member is operatively associated with the threshold member to aid in removing the floc material.
Preferably the above apparatus is a fine solids separator adapted to remove fine solids.